1. Field of the Invention
The present invention relates to a zoom lens suitable, for example, such as a digital still camera, a video camera, a security camera, a broadcast camera and a silver-halide film camera.
2. Description of the Related Art
A wide angle of view, a high zoom ratio and a high optical performance in the entire zoom range zoom lens is demanded for an image-pickup lens for an image-pickup apparatus.
A five groups zoom lens comprising, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power is known (U.S. Pat. No. 8,169,711, U.S. Pat. No. 8,331,034).
If a zoom lens having five lens units of the above refractive power arrangements makes the focal length of the telephoto end longer so as further to achieve high zoom ratio, maintaining of high optical performance is difficult since aberration such as spherical aberration, astigmatism, and chromatic aberration in the zoom range of the telephoto end increases. Additionally, if refractive power of each lens unit is stronger so as to make the entire system smaller, correction of aberration such as axial chromatic aberration, chromatic aberration of magnification and comatic aberration at the telephoto end is difficult since a lot of the above aberration generate.